This invention relates to solids handling and is particularly concerned with an apparatus for removing solids from a solids upflow vessel, such as a vertical solids upflow retort used for pyrolyzing kerogen-containing oil shale to produce hydrocarbon liquids and gases.
It is known to retort oil shale and other hydrocarbon-containing solids by a technique of contacting upward flowing, hydrocarbon-containing solids with downflowing gases in a vertical retort. One such technique is disclosed in U.S. Pat. No. 3,361,644, the disclosure of which is hereby incorporated by reference in its entirety. To produce product vapors, the upward-moving bed of shale particles exchanges heat with a downflowing, hydrocarbonaceous and oxygen-free eduction or retorting gas of high specific heat introduced into the top of the retort at a temperature between about 950.degree. F. and about 1200.degree. F. In the upper portion of the retort, the hot eduction gas pyrolyzes the shale, thereby producing hydrogen and hydrocarbonaceous vapors. In the lower portion of the retort, the eduction gas preheats the ascending bed of hydrocarbon-containing particles to pyrolysis temperatures. As preheating continues, the eduction gas steadily decreases in temperature, condensing high boiling hydrocarbonaceous vapors into a raw oil product while leaving a product gas of relatively high BTU content. The oil and product gas are then separated, and a portion of the product gas is heated and recycled to the top of the retort for use as the eduction or retorting gas.
A number of different devices and methods for introducing particulate solids into the bottom of vertical retorts and other solids upflow vessels have been proposed. U.S. Pat. Nos. 3,361,644 and 4,249,855 disclose a solids feeding apparatus and method in which solids are introduced upwardly into the bottom of a vertical retort by means of a piston reciprocating in a feed cylinder that is oscillated between an outlet of a solids feed reservoir and the bottom solids inlet of the retort. U.S. Pat. Nos. 3,908,865 and 4,037,736 disclose solids feeding devices and methods in which particulate solids are introduced upwardly into the bottom of a vertical solids upflow vessel by means of twin pistons reciprocating in twin feed cylinders that are oscillated between one or more solids feed chutes and the bottom solids inlet of the solids upflow vessel.
A major problem associated with the solids upflow systems described above is that there is no fully satisfactory method for removing the solids from the solids upflow vessel during maintenance turnarounds. The most commonly encountered system for removing solids from upright vessels consists of nozzles welded onto the bottom of the vessel or onto the side of the vessel near the bottom. This approach, however, is unsatisfactory in the case of the systems described above. Nozzles cannot be located at the very bottom of the upflow vessel because they would interfere with the oscillation of the feeding device between the outlet of the feed reservoir and the bottom solids inlet to the retort. Moreover, installing nozzles on the sides of the retort near the bottom would be difficult and costly because of all the other equipment that surrounds the retort in this area. If the nozzles were located higher on the sides of the retort above the other associated equipment, the entire vessel could not be emptied by draining the solids through the nozzles. Some solids would remain in the vessel below the level of the nozzles. In addition, if nozzles were used, it would be difficult to control the flow of the solids out of the vessel without the use of relatively expensive solids flow controlling devices.
Accordingly, it is one of the objects of the present invention to provide an apparatus for removing substantially all solids from a solids upflow vessel without the use of drainage nozzles. It is another object of the invention to provide an apparatus for inexpensively controlling the rate of flow of solids as they are removed from a solids upflow vessel. These and other objects of the invention will become more apparent in view of the following description of the invention.